Adjustable transformer core clamp



E. s. ALDRIDGE, JR 3,419,836

ADJUSTABLE TRANSFORMER CORE CLAMP Dec. 3l, 1968 Sheetof 2 Filed July 26, 1967 @@@QOO Dec. 31, 1968 F. S. ALDRIDGE, JR

ADJUSTABLE TRANSFORMER coRE CLAMP Sheet Filed July 26, 1967 /NVENTOR /C'A/v/f 5. Aw /aGgJ/Q. BY

rroR/vfy United States Patent O 3,419,836 ADJUSTABLE TRANSFORMER CORE CLAMP Frank S. Aldridge, Jr., Rome, Ga., assignor to General Electric Company, a corporation of New York Filed July 26, 1967, Ser. No. 656,184 6 Claims. (Cl. 336-210) ABSTRACT OF THE DISCLOSURE A rectilinear portion of a laminated magnetic core which is clamped laterally between parallel longitudinal clamps is also clamped endwise between transverse plates which extend between overhanging ends of the longitudinal clamps in abutting relation with the ends of the core portion. The transverse plates are pressed against the core ends by angularly adjustable eccentric collars mounted on transverse ti'e rods adjacent the plates.

This invention relates to stationary electrical induction apparatus, and more particularly to an improved adjustable core clamp for power transformers.

Power transformer cores are generally comprised of a plurality of vertical leg portions formed of stacked laminations of magnetizable material and a pair of upper and lower horizontal yoke portions joining the ends of the legs and similarly formed of stacked laminations. Typically the yoke laminations are clamped together laterally between pairs of channel-shaped yoke clamps, and the leg laminations are clamped together laterally between pairs of longitudinally extending tie plates, the ends of which are bolted or pin-connected to the upper and lower yoke clamps.

With such a strucure, there exists the possibility that some of the laminations, and especially the yoke laminations, may shift longitudinally with respect to each other or with respect to the yoke clamps. Such shifting is most likely to occur, if at all, during building or shipping operations or as a result of high stresses set up by electrical short circuits in operation. In order to prevent undesirable shifting of core laminations, and to reduce core loss and noise which might otherwise result from looseness of the laminations, it is desirable to clamp core laminations longitudinally as well as laterally in the yoke or other rectilinear portions of a magnetizable core.

Large laminated cores of induction apparatus are frequently provided with overlapping mitered corner joints, as shown for example in Patent 3,214,718-Graham- In such cores the intended overlap must be large enough to allow for machine tolerances on miter-cut sheets as well as for possible displacement in handling and shipping. To minimize core loss in grain-oriented cores, it is desirable that this corner overlap be as small as possible. As machine capability for accurate cutting of laminations is improved, it becomes more imperative that reliable means be provided for longitudinal clamping of core sections.

Accordingly, therefore, it is a principal object of this invention to provide improved clamping means for laminated miagnetizable cores in electrical induction apparatus such as power transformers and the like.

It is a more particular object of the invention to provide adjustable means for endwise, or longitudinal, clamping of core laminations in high power electrical induction apparatus.

In carrying out my invention in one preferred embodiment, I provide a rectilinear portion of a laminated magnetizable core with a pair of parallel longitudinal clamping bars or channels bolted together to compress the core laminations laterally. Between the longitudinal clamping bars, and in endwise .bearing engagement with opposite ends of the laminated rectilinear core portion, I provide a ICC pair of transversely extending clamp-ing members, preferably formed as rigid plates or channels. Closely adjacent the outer sides of these transverse clamping members, I provide tie rods or bolts between the longitudinal clamping bars, preferably having several such tie rods adjacent `each transverse clamping plate and in parallel spaced relation therewith. Upon these tie rods I mount adjustable wedging members which engage the transverse clamping plates and press firmly against the ends of the core portion. Preferably these adjustable wedges are in the form of eccentric collars angularly adjustably positioned on the tie rods to press the transverse clamping plates firmly against opposite ends of the core portion.

My invention will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing in which:

FIG. 1 is a partly broken-away side elevational view of a power transformer core illustrating one embodiment of my improved core clamp;

FIG. 2 is an end elevational view, partly in section, of the transformer core of FIG. l;

FIG. 3 is a partially exploded view of one corner of the transforme-r core of FIG. 1;

FIG. 4 is a top view, partly in section, of the transformer core of FIG. l;

FIG. 5 is a side view, partly in section, of one corner of the transformer core of FIG. l; and

FIG. 6 comprises plan and elevational views of one form of adjustable wedge for the core clamp of my invention.

Referring now to the drawings and particularly to FIGS. l, 2 and 3, a power transformer is therein illustrated having three leg portions 10, 11 and 12 joined by a bottom yoke portion 13 and a top yoke portion 14. The several core portions are formed from stacked laminations of magnetizable material. Each rectilinear portion of the core has a cruciform cross section (as illustrated in FIG. 3), and is provided with interior -central ducts 16 and 17 extending therethrough. The duct 16 completely separates the front half of the core from the back half of the core for the purpose of circulation of the cooling fluid, and the proper spacing between the core halves is provided by spacers 18. The duct 17 extends through the core perpendicular to the planes of the laminations and at right angles to the duct 16, providing improved magnetic characteristics for the core and a path for the circulation of cooling fluid. In the fully split type of core illustrated, clamping bolts 25 extending through the yokes and legs pass through the ducts 17. The core legs and yokes preferably have mitered corner joints (not shown), although other well known types of joint such as a butt or lap joint may be used without departing from the scope of this invention. Similarly other core cross-sectional configurations may be employed with the core clamp of this invention.

For the sake of clarity, windings 19, 20 and 21, positioned on the core legs 10, 11 and 12, respectively, are shown only in phantom by means of broken lines.

In order to hold the core laminations lirmly together, a pair of channel-shaped clamping bars 23 are provided along opposite outer faces of the lower yoke laminations and a pair of channel-shaped clamping bars 24 are provided along opposite outer faces of the upper yoke laminations. In addition, each vertical leg (10, 11, 12) is provided with a pair of tie bars 22 on opposite sides thereof, and each tie bar is connected at opposite ends to the upper and lower yoke clamps, respectively. Clamping bolts 2S extending transversely through the leg and yoke laminations clamp together cooperating pairs of yoke clamps 23 and 24 and cooperating pairs of tie bars 22.

A bolt may also be utilized to connect the ends of the tie bars 22 to the yoke clamps 23 and 24. Preferably, however, a pin and slot type connection 26, 27 is provided between .the tie bars and the yoke clamps, as 1s shown herein and more fully described and claimed in Patent 2,910,663-Wilk et al. To provide space for circulation of fluid around the core in close contact with the laminations, a plurality of spacing blocks 28 are positioned between the sides of the yoke laminations and the top and bottom yoke clamps 23, 24.

As previously explained, the upper and lower yoke clamps are connected together independently of the leg laminations by means of the tie plates 22. For added strength in the entire structure, reinforcing plates 29 are welded between the flanges of the channel-shaped yoke clamps in the region of their connection to the tie plates 22. Additionally the yoke clamps extend horizontally beyond the ends of the yoke laminations, and additional tie rods or clamping bolts 30 extend between the pairs of yoke clamps in these extended regions.

To facilitate lifting of the transformer, the upper yoke clamps are provided with several lifting lugs 31. For further rigidity, short transverse clamping plates or channels 32 extend across the ends of the yoke laminations between the yoke clamps and in the small space between the ends of the yoke laminations and the external tie rods 30. The transverse end plates 32 abut against the opposite ends of the yoke laminations, a sheet of insulating material 33 preferably being interposed to prevent short circuiting of the laminations. The external tie rods 30 are closely adjacent and parallel to the outer faces of the transverse clamping plates 32.

In order to yclamp the rectilinear yoke portions of the core firmly against endwise or longitudinal displacement between their respective pairs of yoke clamps 23, 24, I provide adjustable wedging means at the outer side of each transverse end clamp 32. So that existing structure may be utilized to the fullest extent,` I interpose such wedges between the outer surfaces of the clamping plates 32 and the closely adjacent external tie rods 30 which extend between the overhanging ends of the yoke clamps. As illustrated, my preferred form of adjustable wedging means consists of a pair of eccentric collars 34 loosely mounted in spaced-apart relation on each tie rod 30. The collars 34 are angularly adjustable on the rods 30, and to this end each is provided with a radially extending arm 34a for cooperation with an adjusting stud 35 iixed to the juxtaposed clamping plate 32. Such an eccentric collar is shown in plan and elevational views at FIG. 6, and a plurality of such collars are shown in operative position on the several tie bolts 30 shown in FIGS. 145. Each wedging collar 34 is formed with a circular outer periphery and an eccentric bore. The radial positioning arm 34a is slotted longitudinally and extends radially from the collar in the line of the diameter through the eccentric bore and from the side opposite the eccentric bore.

As shown in FIGS. 1-5, each tie bolt 30 is provided adjacent each end and immediately on the inner side of each yoke clamp (23 or 24) with an eccentric wedging collar 34 having its radial arm 34a at the position of maximum radius. The collars 34 are so positioned that their arms 34a extend inwardly and generally parallel to the outer surface of the adjacent transverse clamping plate 32. Each adjusting stud 35 extends through the slot in the positioning arm 34a of the juxtaposed wedging collar 34, and a nut 35a on the stud acts adjustably to draw the arm 34a inwardly toward the clamping plate 32 and thus to increase the wedging action. In this way the clamp ing plates 32 are forced inwardly against the ends of the rectilinear yoke portions 14 of the core by wedging action between the transverse clamping plates 32 and the adjacent tie rods 30.

It will now be understood that w-hile I have shown and described a preferred embodiment of my invention by Way of illustration, various modifications will occur to those skilled in the art. l therefore wish to have it understood that I intend in the'appended claims to cover all such modiiications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure byV Letters Patent of the United States is: v l

1. In 'an electric induction apparatus, a laminated magnetic core including a rectilinear portion, said portion comprising a plurality of laminations extending longitudinally thereof in parallel flatwise engaging relation, means for compressing said laminations laterally including a pair of longitudinal clamping bars extending along opposite outer faces of said laminations and beyond both ends of said core portion, a pair of transverse clamping plates extending between said clamping bars and abutting against opposite ends of said core portion, a tie rod betweenl said clamping bars adjacent the outer side of each said clamping plate, and adjustable wedging means interposed between each said tie rod and the juxtaposed transverse clamping plate.

2. An electric induction apparatus according to claim 1 wherein said wedging means comprises an eccentric collar loosely mounted for angular adjustment upon said tie rod.

3. An electric induction apparatus according t0 claim 2 wherein said eccentric collar is provided with a radially extending positioning arm, and adjustable positioning means are provided to retain said arm in a selected angular position.

4. An electric induction apparatus according to claim 1 wherein two parallel tie rods are positioned adjacent each said transverse clamping plate, and said wedging means comprises two eccentric collars loosely mounted for angular :adjustment in spaced-apart relation on each said tie rod.

5. In an electric induction apparatus according to claim 4 wherein each said eccentric collar is provided with a slotted radial arm extending generally parallel to the plane of the juxtaposed transverse clamping plate, means for adjustably angularly positioning each said slotted radial arm comprising a threaded stud and nut mounted on the adjacent transverse clamping plate and engaging said arm through the slot therein.

6. In an electric induction apparatus, a laminated magnetic core comprising a pair of rectilinear yoke members in panallel spaced relation and at least two leg members interposed perpendicularly therebetween, a pair of rigid yoke clamps extending along and beyond each said yoke member, each said pair of yoke clamps being bolted together transversely of the yoke laminations, a pair of tie members extending #along opposite sides of each said leg member, opposite ends of each said tie member being xedly connected to one yoke clamp of each said pair of yoke clamps, a transverse clamping plate extending across each end of each said yoke member between the associated yoke clamps `and in abutting relation with one end of the associated yoke member, a pair of tie rods extending between each said pair of yoke clamps adjacent the outside surface of each said transverse clamping plate, land a pair of angularly adjustable eccentric cams mounted in spaced-apart relation on each said tie rod in wedging engagement with the juxtaposed transverse clamping plate.

References Cited UNITED STATES PATENTS 1,406,245 2/1922 ThOrdarsOn 336-2l0 3,156,885 1l/1964 Koza 336-210 XR FOREIGN PATENTS 871,868 7/1961 Great Britain.

LARAMIE E. ASKIN, Primary Examiner'.

T. I. KOZMA, Assistant Examiner. 

